Multi-layer acoustical plaster system

1. An acoustical system to be applied to a substrate, comprising:

a base layer mixture that adheres to the substrate, consisting of a first binder, a first thickener and a plurality of first particles, and optionally acoustically absorbent fibers and water, wherein said first particles consist of porous, lightweight, non-close packing particles having a first mean diameter, wherein said first mean diameter is from about 1000 microns to about 5000 microns, and wherein the amount of said first particles in the base layer mixture is from 8 to 45%, wherein the first particles are selected from the group consisting of expanded perlite, coated expanded perlite, glass microspheres, resin microspheres, blown glass beads, gas-filled resin spheres, polystyrene particles, gas-filled inorganic spheres, hollow or porous inorganic beads, polybutadiene particles, rubber particles, elastomeric particles and combinations thereof; and

a finish layer mixture that adheres to said base layer mixture, said finish layer consisting of a powder latex binder, a second thickener and a plurality of second particles, and optionally a hydraulic component, water and a set retarder, wherein said second particles consist of porous, lightweight particles having a second mean diameter, wherein said first mean diameter is larger than said second mean diameter, wherein said second mean diameter is from about 100 microns to about 500 microns and wherein the amount of said second particles in the finish layer mixture is from 50% to 80%, and wherein the second particles are selected from the group consisting of expanded perlite, coated expanded perlite, glass microspheres, resin microspheres, blown glass beads, gas-filled resin spheres, polystyrene particles, gas-filled inorganic spheres, hollow or porous inorganic beads, polybutadiene particles, rubber particles, elastomeric particles and combinations thereof.

2. The system of claim 1 wherein said first particles and said second particles are selected from the group consisting of expanded perlite, coated expanded perlite, glass microspheres, resin microspheres, blown glass beads, gas-filled resin spheres, polystyrene particles, hollow or porous ceramic beads, polybutadiene particles, rubber particles and combinations thereof.

3. The system of claim 1 wherein said base layer mixture includes the acoustically absorbent fibers.

4. The system of claim 3 wherein said acoustically absorbent fibers comprise at least one of the group consisting of mineral wool, cotton, fiberglass, wood pulp and combinations thereof.

5. The system of claim 1 wherein said finish layer mixture includes the hydraulic component.

6. The system of claim 5 wherein said hydraulic component comprises calcined gypsum.

7. The system of claim 5 wherein said finish layer mixture includes water and the set retarder.

8. The system of claim 1 wherein each of said base layer mixture and said finish layer mixture includes water.

9. The system of claim 1 further comprising a cushion layer that adheres to the substrate and to which said base layer mixture adheres.

10. The system of claim 9 , wherein said cushion layer is selected from the group consisting of a mastic, an adhesive, a viscoelastic and a setting type cementitious material, said cushion layer having a viscosity of between 90,000 to 210,000 cps at room temperature.

11. The acoustical system of claim 1 , wherein the substrate is selected from the group consisting of wood, metal, cast concrete, brick, wood boards, cellulosic particle composite boards, cementitious boards and paper-faced mineral panels.

12. A method of using the acoustical system of claim 1 , the method comprising:

a) applying the base layer mixture of claim 1 to a substrate;

b) allowing said base layer mixture to harden to form a base layer;

c) applying the finish layer mixture of claim 1 to said base layer;

d) allowing said finish layer mixture to harden to form a finish layer.

13. The method of claim 12 wherein said substrate is panel free.

14. The method of claim 12 wherein step d) comprises allowing said finish layer mixture to set.

15. The method of claim 12 wherein step d) further comprises floating or troweling the finish layer.

16. The method of claim 12 further comprising spreading a cushion layer onto the substrate prior to step a).